1. Field of the Invention
The present invention relates to a digital camera, and relates particularly to the art of automatic light adjusting control for flash-assisted photography.
2. Description of the Related Art
In digital cameras that generate image signals of a photographic subject by receiving and photoelectrically converting the light from a photographic subject via an image sensor, adjustment of the exposure level is accomplished using image signals obtained by the image sensor.
When flash illumination is employed when taking a photograph using a digital camera, flash light feedback control cannot be performed using the image signal photographed by the flash light because the image signal is obtained by outputting a load after the photograph is taken.
For this reason, in conventional digital cameras, a light adjusting control sensor is provided on the digital camera body for directly sensing external light, and an external light adjusting control method is used to control the flash emission based on the amount of light detected by the light adjusting control sensor. Alternatively, a leading method is pre-flash type light adjusting control which performs a pre-flash illumination immediately before photography and controls the flash emission during photography based on the image signal obtained during the pre-flash illumination.
In light adjusting control accomplished by means of the previously mentioned external light adjusting control sensor, the external light directly enters the light adjusting control sensor without mediation of a photographic lens, whereas light from a photographic subject enters the image sensor through a photographic lens such as a zoom lens or the like. For this reason the field angles are mutually different, and the light adjusting control range and the photographic range do not match so as to disadvantageously reduce light adjusting control accuracy.
In pre-flash type light adjusting control, the field angles match because the image sensor functions as the light adjusting control sensor. However, since two flash emissions are required for the pre-flash illumination and the main photography flash illumination, there is a disadvantageous time lag between light adjusting control time and the photography time.